Electric motor controller



Feb. 29, 1944. I NEWMAN 7 2,342,961

ELECTRIC MOTOR CONTROLLER Filed July 16, 1942 .L1 Baal La R9 1 V 150 v2E2 F X I i H {1M0- V V l 3A 2A MS L l HOIST LOWER I oFF 545:1 12345 W Li E l HM -0 l iil NIH: ]-I5 )7 ii'o oLii '5 l8 1 l l I K I iIIlI/Kllll?1 j o: CON-FACTOR CLOSED 9: SPRING CLOSED es CONTROLLED BY 16R a)CONTROLLED BY VR Patented Feb. 29, 1944 ELECTRIC MOTOR CONTROLLER JohnM. Newman, Wauwatosa, Wis., assignor to I Cutler-Hammer, Inc.

Milwaukee, Wis., a cor, poration of Delaware Application July 16, 1942,Serial No. 451,152 9 Claims. (01. 172-152) This invention relates toimprovements in controllers for motors in crane hoist and similarservice.

In Patent No. 2,288,133, issued June 30, 1942, there is disclosed acontroller for crane hoists, and the present invention while not limitedthereto is especially applicable to such type of controller.

The controller of the aforementioned patent provides for operating adirect current motor as a series motor for hoisting and as a shunt motorfor lowering and provides for dynamic braking of the motor underoverhauling load conditions. Also it provides for high speed lowering atsubstantially the same speed whether the load is heavy and overhaulingor whether the hook is empty. In most instances it is desirable tomaintain power connections for the motor throughout lowering and saidpatented controller is designed to maintain such connections.

n the other hand, it has been found desirable in certain instances, aswhere the system employs a Diesel engine or the like as a prime mover,to prevent the motor when driven by its load from pumping back currentto the line, and the present invention has among its objects to providea controller having substantially all the advantages of the controllerof said patent but which will afford protection against pumping back ofcurrent by the motor.

Another object is to effect the desired control with but slightmodification of said patented control.

Another object is to utilize for controlling disconnection from the linein lowering a relay serving to control for uniform high speed loweringunder the different load conditions hereinbefore mentioned.

Other objects and advantages of the invention will hereinafter appear.

The present invention because of ease of embodiment in theaforementioned earlier controller has been so illustrated in theaccompanying drawing which will now be described, it being understoodthat the invention is susceptible of embodiment in other forms withoutdeparting from the scope of the appended claims.

In the drawing,

Figure 1 is a diagrammatic view which for simplicity of illustrationomits numerous details and control circuits now known to the art, and

Fig. 2 is a chart showing the sequence in which the switches orcontactors shown in Fig, 1 are to be operated.

Referring to Fig. 1 of the drawing it shows a motor M having an armatureA and a field winding F to be connected to lines L L. in series relationfor hoisting and in shunt relation for lowding. These and otherconnections for the motor are made by switcheswhich in type and numberare the same as in the controller of the patent aforementioned, and aswill be understood these switches are to be assumed to be operated byelectroresponsive windings although in most instances the switches arehere shown without windings for simplicity of illustration. In mostinstances the control of these switches is the same as in the controllerof the patent aforementioned and in the drawing hereof such commoncircuits as well as the master switch contacts have for simplicity ofillustration been omitted except where illustration has been made toclarify the modification here involved.

Switches M and H provide for connection of the motor armature and fieldwinding in series to lines L and L through resistors R, R R, R and R inseries for hoisting, resistor R being shunted throughout hoisting byswitch I which is biased to closed position and switch 2DB being openinstead of closed as shown. Resistors R R and R3 are adapted to beshunted progressively by switches 2A, 3A and A, respectively, theseswitches closing sequentially as shown by the chart Fig. 2 under thecontrol of contacts (not shown) of master switch MS and certain of saidswitches preferably having a. definite time element incident to closure.Thereafter as indicated by saidchart, switches 5A and 6A may be closedto shunt resistors R and R preferably subject to control to render theirclosure sequential and each subject to a definite time element. Thusprovision is made for acceleration and speed control in hoisting inaccordance with earlierpractice, the indicated closure of switch IKO inthe first and second hoisting positions being here neglected but laterdiscussed.

Switches M, IKO and IDB, here neglecting switch 2DB and the circuitcontrolled thereby, provide for connection of the motor armature andfield winding in parallel to lines L and for lowering. Switch IKOestablishes a circuit from line L through resistor R to the motor M at apoint between its armature and field winding. From the other side of thearmature circuit extends to and through resistors R and R to and throughthe coil of a relay VR in parallel with resistor R to and through coil 0of relay ICR and thence through switch IDB and switch M to line L. Fromthe right hand terminal of brake coil B to and through resistors R, Rand R and thence through switch IA and switch M to line L As indicatedby the chart, Fig. 2, switches 2A; 3A, 4A, 5A and 6A are closed in thefirst lowering position and thus if switch lA remains closed the motorcircuits are without resistance other than the resistor R common to thearmature and field circuits and the fixed resistance R in the armaturebranch in'parallel with the winding of the relay VR. This is inaccordance with earlier practice, as is also opening of switches 4A, 5Aand 6A in the second lowering position and opening of switch 3A in thethird lowering position, all as indicated by the chart Fig. 2, first toinclude in the armature circuit resistors R and R and in the fieldcircuit resistor R and then to include in the field circuit resistor RMeanwhile switch IA remains closed for its operating winding iscontrolled by normally disengaged contacts 2I of the master switch MS,which contacts are not engaged until the master switch is moved to itsfifth lowering position. As will be understood, the positions of themaster switch which effect engagement of its contacts disengaged in oilposition are indicated by circles and thus as there is but one circle inline with contacts 2i it will be understood that said contacts shown asdisengaged will remain in that relation except in the fifth loweringposition later to be discussed.

As in the controller of the patent aforementionedand as indicated by thechart Fig. 2, the switch 2DB closes only in the off position of themaster switch. When closed the switch 2DB completes a dynamic brakingloop extending from the left hand terminal of the motor armature A toand through switches 5A and 6A to and through the winding of relay VRand parallel resistance R' and thence to and through the winding ofrelay ICE and the contacts of switch IDB to the .right hand terminalofmotor field winding F.

This connects the motor armature and field winding in series for dynamicbraking with the brake coil B excluded from circuit. As in the earliercontroller and as shown by the chart Fig. 2 the switches A and 0A arenow subject to control by the relay VR for graduation of dynamic brakingas the motor comes to rest.

Now considering the provisions departing from the earlier control andagain considering control for lowering, the relay ICR has been given thedual function of controlling switch IA and controlling switch IKO. Morespecifically the relay ICR which as in the earlier control is closed inall lowering positions'pending overhauling of the motor opens wheneverthe motor overhauls, but it closed when the master switch MS is moved tofinal lowering position coacts therewith to energize switch IA to insertin the field branch of the motor, resistor R, to afford a high speed foran empty hook substantially the same as the lowering speed under heavyoverhauling load conditions. Also in the control here provided theswitch IE0 is placed under the control of relay ICE in the fourth andfifth lowering positions as indicated by the chart Fig. 2 whereby ifwhenthe motor tends to act as a generator with consequent response ofrelay ICR the switch IKO is caused to open to disconnect the motor fromsupply line L This protects the system against undesired pumping back ofcurrent.

This dual functioning of the relay ICE. is provided for in the followingmanner. The wind- 2,8&2,961

series with the motor armature in lowering and is subject to currentreversals when the motor acts as a generator, whereas the winding 0 ofsaid relay is subjected to only a unidirectional flow of current beingconnected across the line in series with the winding of under-voltageswitch UV for energization continuously under normal conditions. Thusprovision is made'for the aforedescribed action of relay ICR per se. Thecircuit for switch IA controllable by relay ICR extends from line Lthrough contacts 2I of the master switch MS but only when in its lastlowering position by conductor III to and through the winding 0 ofswitch IA by conductor II through auxiliary normally open contacts I2 ofswitch 6A by conductor I3 through the contacts of relay ICR to line L Asshown there is a parallel circuit from conductor I3 through normallyclosed auxiliary contacts ll of switch 2K0 by conductor I5 to line U butthis parallel circuit is interrupted in the fourth and fifth loweringpositions because of energization of the switch 2K0 as shown by thechart Fig. 2, wherefore the switch IA is under the control of the relayICR alone in the fifth lowering position. The circuit for switch IKOcontrollable as aforedescribed by the relay ICR extends from line Lthrough the contacts 20 of the master switch MS in all loweringpositions by conductor I6 through normally open auxiliary contacts H ofswitch M, by conductor I8 to and through the contacts of relay ICE. toline 1 Alternatively circuit may be traced from conductor I8 byconductor I3 through the normally closed contacts ll of the switch 2K0to line L and thus as the switch 2K0 is not energized except in thefourth and fifth lowering positions its auxiliary contacts I4 renderenergization of the switch IKO independent of relay ICR. in the firstthree lowering positions but subject to control by said relay in thefourth and fifth lowering positions.

While the provisions just described prevent the relay ICR. fromdeenergizing the switch IKO to disconnect the motor from line L exceptin the fourth and fifth lowering positions it may in someinstances bedesirable for power saving or for other reasons to have switch IKO underthe control of relay ICR. in all lowering positions. Where this isdesired it is only necessary to omit the auxiliary contacts it of switch2K0.

With the modified control thus far discussed the speed torquecharacteristics are not as good as in the earllercontrol aforementioned,but substantially like characteristics have been found obtainable byproviding as shown an armature shunt including a resistor R to by-passfrom the motor field part of the armature current under overhauling loadconditions. While the resistor R is shown as having permanent connectionin the power circuit it is to be understood that it might have controlmeans to make and interrupt its connection as desired, and that itslocation in circuit is susceptible of change. However, its .location asillustrated has been found advantageous especially in minimizing itseffect in both lowering and hoisting positions other than in: 0 of relayICE is connected at all times in hoisting positions.

What I claim as new and desire to secure by Letters Patent is:

1. In control for hoist motors, the combination with means selectivelyto establish power connections for hoisting or power and dynamic brakingconnections for lowering and to aflord speed control, of means to rendersubstantially uniform under heavy and light loads a high lowering speedselectable by the first mentioned means and to effect through the mediumof said first power connections at certain of the lowering' aasacerspeeds when the load is overhauling, the second mentioned meanscomprising a relay which is subject to control by dynamic brakingcurrent and which renders said second mentioned means automatic inperforming both aforemention 7 functions thereof.

3. In control for hoist motors, the combination with means selectivelyto establish power connections for hoisting or power and dynamic brakingconnections for lowering and to afford speed control, of means to rendersubstantially uniform under heavy and light loads a high lowering speedselectable by the first mentioned means and to eflect through the mediumof said first mentioned means interruption of lowering power connectionsat certain of the lowering speeds when the load is overhauling, thesecond mentioned means having for rendering the same automatic inperforming both aforementioned functions thereof a relay with controlwindings connected in circuit in lowering to act diflerentially orcumulatively according to the weight of the load. 7

4. In control for hoist motors, the combination with means selectivelyto establish power connections for hoisting or power and dynamic'bralring connections for lowering, said means aflording any one of anumber of speeds in hoisting or lowering and having anelectro-responsive switch through which it tends at all lowering speedsto maintain said lowering power connections, of a' relay to control saidswitch for action thereof to interrupt power connections at certain ofthe lowering speeds when the load is overhauling, said relay having aplurality of control windings one of which is subjected to aunidirectional fiow of current regardless of load conditions and anotherof which is traversed by current changing in direction of flow accordingto whether the load is light or overhauling.

5. In control for hoist motors, the combination with means selectivelyto establish power connections for hoisting or power and dynamic brakingconnections for lowering, said means affording any one of a numberof'speeds in hoist- 1 ing or lowering and having an electro-respcnsiveswitch through which it tends at all lowering speeds to maintain saidlowering power connections, of a relay to control said switch for actionthereof to interrupt power connections at certain of the lowering speedswhen the load is overhauling, said relay having a plurality of controlwindings one of which is subjected to a unidirectional flow of currentregardless of load conditions and another of which is traversed bycurrent changing in direction of fiow according to whether the load islight or overhauling, and means controlled by said relay and the firstmentioned means jointly to afford high speed lowering at substantiallythe same rate whether the load is light or overhauling.

6. In combination a series hoist motor, means selectively to establishpower connections for said motor for hoisting, with the armature andfield winding of the motor in series, or power and dynamic brakingconnections for said motor for lowering, with the motor field shuntingthe armature, means to eil'ect through the medium of the first mentionedmeans during lowering at certain of the lowering speeds, interruption ofpower connections when the load is overhauling and a circuit to by-passfrom the motor field winding some of the armature current for improvedspeed torque characteristics.

7. In control for hoist motors, the combination with means selectivelyto establish power connections for hoisting or power connections forlowering, said means including a master switch having diflerentpositions for selection of speeds in both hoisting and lowering and saidmeans tending to maintain power connections throughout loweringregardless of the lowering position occupied by said master switch, andmeans eiIective when said master switch is in certain of its loweringpositions to cause the first mentioned means to interrupt powerconnections under overhauling load conditions, but ineilective in otherof the lowering positions of said master switch.

8. In a hoist system having as a prime mover a Diesel engine and havinga hoist motor which under overhauling loads tends to pump back currentwith undesirable eflects on such prime mdver, the combination with motorcontrolling means which establish power connections for lowering andwhich afford a plurality of lowering speeds and tend to maintain powerconnections regardless of overhauling load conditions, of meanseffective under overhauling load conditions at least at certain of thelowering speeds to cause the first mentioned means to interrupt powerconnections, the first mentioned means including means which at certainof the lowering speeds renders the second mentioned means ineffective tofunction as stated.

9. In a hoist system having as a prime mover a Diesel engine and havinga hoist motor which under overhauling loads tends to pump back currentwith undesirable effects on such prime mover, the combination with motorcontrolling means which establish power connections for lowering andwhich afford a plurality of lowering speeds and tend to maintain powerconnections regardless of overhauling load conditions, ofmeans'eflective under overhauling load conditions at least at certain ofthe lowering speeds to cause the first mentioned means k; interruptpower connections, and means which together with the second mentionedmeans provides means affording high speed lowering at substantially thesame rate whether the load is light or overhauling.

JOHN M.

